Optimal power allocation for cognitive radio sensor networks under primary secrecy outage constraint

To secure the primary network, in this paper, we propose a cooperative spectrum access strategy in which the cognitive radio sensor network (CRSN) will cooperate with the primary network to protect the primary confidential messages against malicious eavesdropping and the quality of service (QoS) is supported. In the proposed scheme, the CRSN will exploit its interference on the eavesdropper to secure the primary transmission and as a reward, loose constraint of the spectrum sensing error probability is permitted for the CRSN. According the spectrum sensing results and the activities of primary network, there are four system states in the system. For each state, we will optimally allocate the transmit power of the CRSN so that the average transmission rate of the CRSN is maximized under the secrecy outage probability constraint of the primary network. Moreover, the closed-form expression of the transmit power for each state is derived. Simulation results demonstrate the performance superiority of our proposed strategy over the conventional overlay strategy in terms of SN's average throughput.